j.

CONSULTATIVE DRAFT

DESCRIPTION OF, AND SCHEDULE FOR,

NNWSI TOPICAL REPORTS

Itasca Consulting Group

May 1988

PD-1 WPRES PDR

NNWSI TOPICAL REPORTS

TABLE OF CONTENTS

I. INTRODUCTION

II. THERMOMECHANICAL TOPICAL REPORTS

III. SEAL SYSTEM TOPICAL REPORTS

IV. ESF TOPICAL REPORT

V. SCHEDULE

APPENDIX (Letter from D. Tiktinsky)

l

I. INTRODUCTION

NRC directed Itasca to prepare eleven (11) topical reports (let-ter from D. Tiktinksy to R. Hart, 29 March 1988, see appendix).Additionally, NRC had previously requested Itasca to redirectthree on-going studies from BWIP to NNWSI. This draft attemptsto describe, in a very general manner, the work to be done foreach report and to provide a preliminary work schedule. The top-ical reports are listed in Table I-1. The topical reports havebeen divided into three groups:

(1) thermomechanical;

(2) seal system; and

(3) ESF.

Individual topical reports are described in Sections II, IIIand IV. Detailed outlines for each topical report will be devel-oped at a later date and discussed with NRC, as directed in theletter from D. Tiktinsky. Section V provides a preliminaryschedule based on the assumption that all draft topical reportsbe completed by the end of 1988. (NOTE: The statutory SCP ispresently scheduled for release in January 1989.)

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Table I-1

LIST OF TOPICAL REPORTS

Topical Report

A

B

C

D

E

F

G

H

I

J

K

L

M

Title

Sensitivity Analyses for Key Joint Parameters

Thermal-Mechanical Analysis for NNWSI

The Effect of Dynamic Events on Drifts atNNWSI

Analyses of Alternative Waste EmplacementConcepts on Performance of Drifts and Bore-holes

Sensitivity Study of Variations of Heat Load-ing for a Repository at Yucca Mountain

Stability of Openings During Retrieval

Emplacement Borehole Liner Stability Analyses

Disturbed Zone

Discontinuum Versus Continuum Analyses forNNWSI

Borehole and Shaft Seals in the UnsaturatedZone

Material Selection for Sealing Materials fora Repository at Yucca Mountain

Performance Confirmation Test Needs for Seals

Extrapolation of Short-Term Test Data forLong-Term Seal Performance

Exploratory Shaft Facility DesignN

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II. THERMOMECHANICAL TOPICAL REPORTS

The topical reports which primarily concern mechanical andthermomechanical analyses are listed in Table II-1. The firstthree (3) topical reports were initiated under Task Order No. 005to study issues related to the proposed repository at Hanford.Subsequently, these studies have been redirected to incorporateNNWSI site-specific parameters.

It is clear that there is considerable overlap among the nine (9)reports. The overall objective of the reports is to provide acomprehensive suite of calculations which provide guidance topersons reviewing design/rock mechanics issues in the statutorySCP and supporting documents.

Table II-2 gives a matrix of problem parameters, problem scaleand the topical report which will address variation in the spe-cific parameter. The list of problem parameters is taken fromTables 6-10 through 6-16 of the CDSCP.

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Table II-1

TOPICAL REPORTS INVOLVING THERMOMECHANICAL ANALYSIS FOR NNWSI

STUDY

A

B

C

D

TASK

005-01

005-01

005-01

006-01-Ti

006-01-T2

006-01-T3

006-01-T4

006-01-T5

006-01-Til

DESCRIPTION

SENSITIVITY OFJOINT PARAMETERS

THERMAL-MECHANICALANALYSIS

SEISMIC ANALYSIS

ALTERNATIVE WASTEEMPLACEMENT CONCEPTS

SENSITIVITY INVOLVINGHEAT LOADING

RETRIEVAL STABILITY

BOREHOLE LINERSTABILITY

DISTURBED ZONE

CONTINUUM VSDISCONTINUUM

3

TIME (weeks)Remainin SuQQested

3 6

6

6

3

6

6

E 6 6

F

G

6

6

6

4

H

I

6

4

6

6

46 49TOTAL

T

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Table II-2

MATRIX OF PROBLEM PARAMETERS, PROBLEM SCALE AND TOPICAL REPORTS

EMPLACEMENT DRIFTPARAMETER Vertical Horizontal Vertical Horizontal Access FAR-FIELD

I. IN-SITU CONDITIONS

vertical (eV)

horizontal (0 )

temperature

D

II. PHYSICAL PROPERTIES

grain density

porosity

saturation

bulk density,in-situ ()

bulk density,dry (Pdry)

III. INTACT ROCK-MECHANICAL PROPERTIES

bulk modulus (k)

shear modulus (G)

unconfined strength

(c)

cohesion

friction (¢)

tensile strength(at)

assumed to be 7 Pa for all analyses

ADHC ACD

assumed to be 26'C for all analyses

not used explicitly in any analysis

not used explicitly in any analysis

not used explicitly in any analysis

assumed to be 2.34 (g/cc) in all analyses

not used explicitly in any analysis

I I

I I

not used explicitly in any analysis

Fl Fl

Fl FI

G - (2c cost)/( + in¢) for all analyses

G

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Table II-2 (continued)

EMPLACEMENT DRIFTPARAMETER Vertical Horizontal Vertical Horizontal Access FAR-FIELD

IV. JOINT MECHANICAL PROPERTIES

unstressed aperture

half-closure stress

shear stiffness

normal stiffness

cohesion

residual friction

k)r)

JCSo

JRCO

H

H

AH

AH

AH

AFH

A

A

A

AFG G

H

H

V. ROCK MASS MECHANICAL PROPERTIES

bulk modulus (K) p

shear modulus (G) D

unconfined strength

(an)

cohesion D

friction (4) D

VI. JOINT GEOMETRY

spacing

orientation

persistence

D

D

D D

D D

not used explicitly in any analysis

D

D

D

D

D

ACF

ACF

ACF

G

ACF

ACF

ACF

G

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Table II-2 (concluded)

EMPLACEMENT DRIFTPARAMETER Vertical Horizontal Vertical Horizontal Access FAR-FIELD

VII. THERMAL PROPERTIES

conductivity (k)

coefficient ofthermal expansion

(('3

thermal

capacitance (Cp)

BE

D

BE

BE

D

BE

BE

D

BE

BE BE

D

BE BE

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TOPICAL REPORT A: Sensitivity Analyses for Kev Joint Parametersat NNWSI

Tuff is a highly-fractured rock, and its response to mining andheating will likely be controlled, to a large extent, by the me-chanical response of the joints. An important question at theNevada site is the extent to which the jointing controls rockmass response and which joint properties have the greatest influ-ence on this response.

To address these questions, a parametric analysis will be con-ducted on the room-scale response of the rock mass for the pro-posed NNWSI conceptual design (vertical emplacement mode). Thefollowing joint properties will be examined with respect to theireffect on rock mass response:

(1) friction angle;(2) cohesion;(3) stiffness parameters;(4) roughness; and(5) spacing, attitude, and continuity.

Approximately five (5) weeks of the original eight (8) weeks spe-cified for this task has been spent doing BWIP analyses. A mini-mum of six (6) weeks is suggested to perform the analyses forNNWSI. Therefore, an additional three (3) weeks are required be-yond the three (3) weeks remaining. Mark Christianson is theprincipal investigator for this report.

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TOPICAL REPORT B: Thermomechanical Analysis for NNWSI

A detailed analysis of the emplacement hole and thermal and me-chanical response of the rock mass at NNWSI is being performedusing FLAC/STRES3D. The following problems are to be examined:

(1) the thermal regime around the emplacement boreholefor horizontal and vertical emplacement schemes;and

(2) the temperatures at various times at points of in-terest (i.e., emplacement and access drifts).

Approximately three (3) weeks remain in this task. Due to thereduced scope of this task (compared to the original task out-lined for BWIP), this time is considered sufficient. Mark Boardis the principal investigator for this report.

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TOPICAL REPORT C: The Effect of Dynamic Events on Drifts atNNWSI

Evaluation of the effects of dynamic events at NNWSI must addresstwo types of events:

(1) natural seismicity (earthquakes); and

(2) underground nuclear explosions (UNEs).

Both event types will be studied as part of this task. Eachevent type has distinctly different time histories and it willfirst be necessary to develop "typical" time histories for eachevent type. The development of time histories will be based onliterature review and will take roughly one week for each eventtype. The analyses will be performed using UDEC, and the resultswill be compared to empirical observations. Only the period dur-ing pre-closure will be studied, as drifts will be backfilledduring the post-closure period.

Of particular interest to these studies is whether the stresswaves will cause spalling of rock on the excavation periphery orslip along existing discontinuities. The effects of shotcreteand rockbolts in mitigating the dynamic effects will also be con-sidered.

Two drift excavation geometries (horizontal and vertical emplace-ment) will be examined for each event. Several different eventmagnitudes will be studied in an attempt to define the onset ofsignificant damage. Only one set of joint friction or cohesionwill be studied (primary failure modes are assumed to involvemainly tensile failure). Analyses will be made for the periodimmediately following excavation and at the end of the pre-closure period.

A minimum of six weeks is suggested for this work. Loren Lorigis proposed as the principal investigator.

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TOPICAL REPORT D: Analyses of Alternative Waste EmplacementConcepts on Performance of Drifts andBoreholes

The following alternative waste emplacement concepts have beenproposed:

(1) single canister in short vertical hole (referencedesign);

(2) multiple (up to 18) canisters in long horizontalholes; and

(3) one to three canisters in short horizontal holes(see CDSCP, p. 6-4).

The first week of this study period will be used to review thelatest concepts concerning various waste emplacement options.Numerical analyses using STRES3D will be used to evaluate temper-atures and stresses in the rock mass surrounding boreholes. Nu-merical analyses using HEFF will be used to evaluate temperaturesand stresses in a rock mass surrounding drifts. Analyses willuse equivalent rock mass elastic properties.

The six (6) person-weeks allotted for this topical report appearsadequate at this time. Barry Brady is proposed as the principalinvestigator.

r

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TOPICAL REPORT E: Sensitivity Study of Variations of HeatLoading For a Repository at Yucca Mountain

Current layouts for both vertical and horizontal emplacementmethods reflect the use of an areal power density of 57 kW/acre(and an initial heat load of 3.03 kW per waste package) CDSCP,p. 6-148]. This areal power density was recommended by Johnstoneet al. (1984) to limit floor temperatures in unventilated verti-cal emplacement drifts to 1000C or less during the first 110years (p. 10). This gross thermal loading (or areal power den-sity) has been used for all subsequent conceptual designs, eventhough the 100CC criteria apparently can no longer be met.Changes in ventilation system concepts have resulted in replacingthe constraint with a tentative design goal of 50 0C at 50 years(see p. 8.3.5.2-1). This tentative design goal requires that thetemperatures be less than 500C at 50 years for horizontal em-placement drifts or vertical emplacement access drifts.

The CDSCP indicates (p. 6-231) that, with the change to this con-stant, the allowable thermal loading could increase above thecurrent design basis of 57 kw/acre. The objective of this topi-cal report is to investigate the combinations of rock massthermal properties and areal power densities that would meet pre-sent tentative design goals.

The first week of this work will involve review of all designgoals which apply to determination of the allowable areal powerdensity. For example, the borehole wall temperature should beless than 235 0C at all times (see p. 6-195). The remaining five(5) weeks will be used to determine conditions of areal powerdensity and rock mass thermal properties which satisfy existingdesign criteria. Bth HEFF and STRES3D will be used for numeri-cal analyses. Possible combinations of thermal loading andthermal properties will be examined with respect to impacts ofopening stability during the pre-closure period.

A minimum of six (6) person-weeks is proposed for this work, withBarry Brady as principal investigator.

Reference

Johnstone, J. Keith, Ralph R. Peters, and Paul F. Gnirk. UnitEvaluation at Yucca Mountain, Nevada Test Site: Summary Reportand Evaluation. Sandia Report SAND83-0372. June 1984.

-13-

TOPICAL REPORT F: Stability of Opening During Retrieval

Analyses will be performed using UDEC and FLAC to study the sta-bility of drifts during retrieval. Cooling is anticipated forretrieval in both horizontal and vertical emplacement methods.The CDSCP indicates that ambient air can be used to cool thehorizontal emplacement drifts, but cooled air will be requiredprior to entry of vertical emplacement drifts (p. 6-337). Thecalculations will start with the conditions expected at 50 yearsfollowing waste emplacement. The calculations will also considerthe effects of temperature changes on emplaced support compon-ents.

A minimum of six (6) weeks is recommended for this work, withMark Mack as principal investigator.

-14-

TOPICAL REPORT G: Emplacement Borehole Liner Stability Analyses

Only the horizontal waste emplacement involves the use of liners.The SCP CDR assumes a 1/2-inch liner thickness (p. B-2). Appen-dix B presents preliminary liner stress analyses based on assumedrock loads and simple ring analysis. These analyses show verylow stress levels (less than 1.5 ksi) for all cases in which 0.5-inch liners were assumed. Corrosion was considered by repeatinganalyses with thicknesses as small as 0.15 inches. Even withthis thickness, stresses in the liner remained below the yieldstress of at least 30 ksi. Although the calculations involvednumerous simplifying assumptions, they do produce the expectedresults. It is difficult to conceive of repository conditionsunder which the liner modeled as a ring would behave inelasti-cally. Consequently, only a few two-dimensional confirmatory an-alyses are assumed.

A potentially more significant scenario involves a liner trans-versed by a fault. Fault movement could result from thermally-induced stresses or a dynamic event. Three-dimensional analysesusing 3DEC and STRES3D are planned to evaluate displacement mag-nitude. In such analyses, the boreholes will not necessarily beexplicitly modeled.

It is suggested that one (1) week of confirmatory two-dimensionalanalyses be followed by three weeks of preliminary three-dimensional analyses. Roger Hart is proposed as the principalinvestigator.

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TOPICAL REPORT H: Disturbed Zone

The NRC GTP on the disturbed zone states that

NRC considers that . . . a disturbed zone of . . .five opening heights for non-circular openings, orfifty meters, whichever is largest, from any under-ground opening, excluding surface shafts and boreholes,may be the minimum appropriate distance for use in cal-culations of compliance with the pre-waste emplacementgroundwater travel time criterion (lOCFR60.113(a)(2))[Draft GTP: Interpretation and Identification of theDisturbed Zone in the High Level Waste Rule (1OCFR60),June 20, 1986, p. 17).

The GTP goes on to state that DOE should calculate the extent ofthe disturbed zone and discusses some effects that should be ac-counted for in the analyses. It should be noted that DOE "willjustify a definition for the disturbed zone as a boundary 10m orless below any underground opening . . . (CDSCP, p. 8.4-66).

Analyses to be performed for this topical report will be limitedto the consideration of stress redistribution and thermomechani-cal effects around vertical emplacement drifts. Numerical analy-ses will be performed using UDEC, together with joint constitu-tive models employing non-linear normal stiffnesses. The non-linear joint normal stiffnesses are required to determine permea-bility changes. The result of these analyses will be plots ofrelative permeability change versus distance from the excavation.Similar plots are contained in Case and Kelsall (1987) and Chris-tianson and Lorig (1988).

A minimum of six (6) weeks is recommended for this work, withMark Christianson as principal investigator.

References

Case, John B. and Peter C. Kelsall. "Modification of Rock MassPermeability in the Zone Surrounding a Shaft in Fractured WeldedTuff," Sandia Report SAND86-7001, March 1987.

Christianson, M. and L. Lorig. "Appendix A: Preliminary Numeri-cal Sensitivity Study of Factors Influencing the Change in Perme-ability in Rock Mass Surrounding a Shaft in Tuff," Appendix toItasca Consulting Group, Document Review 006-01-59 for the U.S.NRC, April 1988.

-16-

TOPICAL REPORT I: Continuum versus Discontinuum Modeling forNNWSI

NNWSI is currently not planning to extensively use discontinuummodeling in performance calculations of the mechanical responseof the rock mass to heating and mining-induced disturbance. [Anexception to this is that the distinct element method is identi-fied for possible use in wedge analysis for emplacement holes(see CDSCP Section 8.3.2.2.6).] Its present approach is to de-velop a continuum constitutive law for tuff which includes non-linear effects of joint behavior. This continuum material modelwill then be examined in light of field data from testing at theES facility.

This task is aimed at determination of the adequacy of a contin-uum versus discontinuum modeling approach for problems at NNWSI.To address this objective, the following questions will be inves-tigated.

1. At what scale of analysis (i.e., emplacement hole,drift, or repository) is it feasible to use thedistinct element method?

2. At each scale, what effect does detail in modelingof joint structure have on the results of thermome-chanical analysis? The tuff has approximately 13fractures/meter at dips of 80 to 90 degrees, withmuch less frequent fracture at the inclinations(see CDSCP Table 6-15, p. 6-61). All of thesefractures do not equally control the overall behav-ior. The question to be addressed is how many ofthese fractures need to be modeled and at whatpoint is a continuum model sufficient for boundingthe rock mass response?

3. What general procedures are necessary for develop-ment of a continuum constitutive law?

An effort of six (6) person-weeks (rather than the previouslysuggested four (4) person-weeks) is suggested for this topicalreport. The reason for this is that the issue of continuum ver-sus discontinuum modeling will continue to be important in theNNWSI project. Mark Board is proposed as principal investigator.

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III. SEAL SYSTEM TOPICAL REPORTS

Topical reports J through M concern various aspects of the sealsystem. It is clear that there is considerable overlap among thefour reports. This may prove sufficient time in which to set upa team that could tackle all four-i.e., we could probably jus-tify the following:

(1) geochemist, 1/2 week on each report;

(2) hydrologist, 1/2 week on each report; and

(3) radionuclide release expert, ???

One very desirable starting point for all four would be a fairlycomprehensive computer literature search, to be done through theUniversity of Arizona library.

Jaak Daemen will be the principal investigator for all seal sys-tem topical reports.

-18-

TOPICAL REPORT J: Borehole and Shaft Seals in the UnsaturatedZone

Unique needs for borehole and shaft seals in the unsaturated zoneare

(1) airflow control;

(2) volume change (shrinkage) control; and

(3) dessication effects.

GTP format should be followed-i.e., essentially review GTP inlight of unique needs imposed by emplacement in unsaturated zone.

We need to review NNWSI sealing documents, identify GTP needs/re-quirements that have been addressed and those that are not ad-dressed.

Analyses in support could (should?) include:

* thermally-driven airflow analysis could rapidly* thermally-driven water (steam?) flow start exceeding* water inflow from surface allowed level of

effort* implications of water level changes?

(Szymanski's report concepts?)

We should identify, review, summarize literature on free drain-age:

(1) a week is the absolute minimum;

(2) 2 weeks may allow preliminary inclusion of discus-sion of geomechanical/thermal/mechanical effects.

For seals, we should identify (locate), review, summarize, criti-cally evaluate relevant literature on seal performance in unsat-urated environment:

* environmental definition: summarize from availableNNWSI reports (1 week?)

* earthen seals: bentonite/clay/crushed tuff perform-ance in airflow/intermittent water flow environment(1-2 weeks?)

-19-

* cement/grout/concrete seals: evaluate performance inairflow/intermittent water flow environment (1-2weeks?)

* rock/water/seal interactions: chemistry (1-2 weeks?)

Manpower Recommendations:

* 1-2 weeks, hydrologist: free drainage (unsaturatedzone, thermal effects, chemical effects)

* 1-2 weeks, geochemist: (cement/bentonite/tuff)

-20-

TOPICAL REPORT K: Material Selection for Sealing Materials

Summarize/review various reports that have presented methodology,basis and testing needs for repository sealing in general(generic).

Identify aspects that distinguish sealing in an unsaturated en-vironment from sealing in a saturated environment.

Discuss implications of unsaturated environment for seal per-formance.

Material selection is likely to lead to generally proposed seal-ants: cementitious (cement, concrete); earthen (bentonite/crushed rock).

Selection methodology should include:

* performance (design) requirements

* material performance parameters

* environmental factors affecting performance

- temperature- humidity, water/air flow- chemistry, rock, water

Presumably, in-situ environment will be obtained from review ofpublished NNWSI documents.

Basis: performance requirements

meet EPA/NRC requirements

independent performance analysis? (probably beyond scope oftask)

make some numerical variations/sensitivity analyses onFernandez et al. (1987)?

bring in performance analysis specialist for one week (crit-ical review of Fernandez et al., 1987; expert judgment modi-fications of numerical conclusions)?

bring in radionuclide release specialist?

-21-

To what extent should basis include major future changes?Szymanski scenarios?

Testing Needs: demonstrate compliance with performance/designobjectives

Performance Criteria: flow -> permeability

Manpower Recommendations:

1 week each, hydrologist and geochemist

-22-

TOPICAL REPORT L: Performance Confirmation Test Needs for Seals

Identify regulatory performance confirmation requirements:

* in general* specifically for seals* specific aspects for unsaturated zone* testing needs* testing schedule

Consideration needs to be given to in-situ testing vs laboratorytesting (respective advantages and disadvantages).

Main aspect for testing requirements will be testing in tuff,which tends to be chemically quite active.

Laboratory testing can start earlier and, most importantly, al-lows closer control of test environment (might miss some unex-pected interaction effects: initiate some in-situ tests ASAP,and design experiments so that they can be continued until perm-anent closure).

Manpower Recommendations:

1 week each, hydrologist and geochemist

I

-23-

TOPICAL REPORT M: EXTRAPOLATION OF SHORT-TERM TEST DATA FORLONG-TERM SEAL PERFORMANCE

Summarize generic strategies that have been proposed and/or de-veloped for:

* extrapolation of long-term repository performance

* specifically, extrapolation of long-term seal per-formance

- natural/manmade analogs- geochemical stability predictions- thermodynamic stability

* accelerated (aging) testing

* testing of artificially-aged/deteriorated seals underranges of (extremes of) expected future conditions

Identify parameters that are likely to change with time and would(might) affect seal performance:

* rock deformation -> seal loading (tectonically-induced/thermally-induced rock alteration/deterior-ation)

* seal deformation (expansion/shrinkage as a functionof expected environment)

* loads on seals (e.g., backfill, thermal)

* wetting/drying cycles

Manpower Recommendation:

2 weeks, geochemist (cement/bentonite/tuff)

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IV. ESF TOPICAL REPORT (Topical Report N - Exploratory ShaftFacility Design)

This topical report will discuss the likely impacts of ESF con-struction on design and operation of the final repository. Be-cause much of the ESF will eventually be incorporated into therepository, construction of the ESF facility is subject to re-quirements of 1OCFR60 (in particular, Section 60.133, AdditionalDesign Criteria for the Underground Facility).

The topical report will include discussion in the followingareas:

(1) review of latest ESF design (such as described inSection 8.4 of the CDSCP);

(2) construction monitoring (blast monitoring, dis-placement monitoring, etc.) which should occur dur-ing ESF construction [see, for example, Cording etal. (1975)];

(3) construction specifications, including review ofsubsurface QA requirements (see, for example,Morrison-Knudson and Fluor, 1987); and

(4) evaluation of potential adverse impacts of con-struction on ability to characterize the site andconstruct repository.

A minimum of six weeks is proposed for this work, with KrishanWahi as principal investigator.

References

Cording, E. J., A. J. Hendron, Jr., W. H. Hansmire, J. W. Mahar,H. H. MacPherson, R. A. Jones and T. D. O'Rourke. "Methods forGeotechnical Observations and Instrumentation in Tunneling,nDepartment of Civil Engineering Department, University ofIllinois at Urbana-Champaign, Report to NSF, UILU-ENG 75 2022,December 1975.

Morrison-Knudson Engineers, Inc. and Fluor Technology Inc. "Sub-surface Quality Assurance Practices," Report Under Contract AC02-83WM46656, AC02-87CH10290, AC02-83CH10140, DOE/CH/46656-07, 1987.

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V. SCHEDULE

Figure V-1 shows the schedule for completing topical reports.The line segments indicate the time period during which work onthe topical report is expected to be on-going. Initials of thePrincipal Investigator are shown above the line segment and thesuggested person-weeks are shown in parentheses below the linesegment.

-26-

Figure V-1

SCHEDULE FOR TOPICAL REPORTS

TOPICALREPORT MAY JUNE JULY AUG SEPT OCT NOV DEC

A IMC

(6)-1

B

C

MB

(3)

ILJL

(6)-1

D IBB

(6)

E IBB

(6)*1

F IMM

(6)I1

G RH(4)

MC

(6)

-1

H I

S.-

-27-

Fig. V-1 (continued)

TOPICALREPORT MAY JUNE JULY AUG SEPT OCT NOV DEC

I

J

I

I

MB

(6)-I

JD

(6)

K

L

IJD

(4)

IJD 1

(4)

JD I

(4)M I

N IKW

(6)I

APPENDIX

LETTER FROM DAVID TIKTINKSY TO ROGER HART

March 28, 1988

UNITED STATESNUCLEAR REGULATORY COMMISSION

WASHINGTON, 0. C. 20555

MAR 28 1988

Mr. Roger Hart Ii

Itasca Consulting GroupP.O. Box 14806_ __ IMinneapolis, Minnesota 55414

Dear Mr. Hart:

ITASCA should perform the following work under task order 001 and 006 of thecontract NRC-02-85-002 in support of the Geotechnical Engineering / Designsection's ongoina work by the staff. These activities involve the preparationof topical reports. ITASCA should be prepared to discuss the topical reportsduring meetings to be held in Rockville, Md. at NRC headquarters afteroutlines and preliminary work are completed. ITASCA should prepare a drafttopical report for the following topics.

1) Analyses of alternative waste emplacement concepts on performance of driftsand boreholes. This topical report should consider the alternative ofFiorizontal versus vertical emplacement for waste canisters for a repository atYucca Mountain. Analyses should he performed as the basis for conclusions inthe topical report. This effort should take no more than 6 person weeks.

2) Sensitivity study of variations of heat loading for a repository at YuccaMountain. This topical report should discuss the impacts on stability of theopenings during operation/retrieval and the effects of varying the areal heatloading on stability. This effort should take no more than 6 person weeksand should be backed up by analyses.

3) Stability of openings durinq retrieval. This topical report should discussthe stability of openings for retrieval for both horizontal and verticalemplacement. Analyses should also be performed to investigate the effects ofheating / cooling a repository and the effect on retrieval. This effort shouldtake no more than 6 person weeks.

4) Emplacement Borehole Liner Stability analyses. This topical report shouldanalyse the effects of rock movement and heat on the stability of the boreholeliner and the subsequent effect on maintaining the retrieval option. In additionthe work performed on this topical report should provide the basis for reviewof DOE's similar analyses. This effort should take no more than 6 person weeks.

5) Disturbed zone. This topical report should provide the basis for review ofthe disturbed zone proposed by DOE for a potential repository at Yucca Mountainfrom the thermonechanical point of view. The NRC GTP on the Disturbed zoneshould be used as a basis for the topical report. Analyses should be performedto back up any conclusions made in the topical report. This effort shouldtake no more than 6 person weeks.

-2-

6) Borehole and Shaft Seals in the Unsaturated Zone. This topical report shoulddiscuss the unique needs for borehole and shaft seals in the unsaturated zone.The NRC GTP on borehole and shaft seals should be used as a guide for thistopical report. In addition, current concepts of free drainage proposed in theCDSCP by DOE should also he covered in the topical report. This effort shouldtake no more than 6 person weeks.

7) Material selection for sealing materials for a repository at Yucca Mountain.This topical report should discuss the methodology, basis and testing needsfor material selection for seals for a repository in the unsaturated zone.This effort should take no more than 4 person weeks.

8) Performance confirmation test needs for seals. This topical report shoulddiscuss what tests are needed during the performance confirmation period forseals in the unsaturated zone. This effort should take no more than 4 personweeks.

9) Extrapolation of short term test data for long term seal perf ormance. Thistopical report should discuss how data which will be obtained durinq arelatively short period of time may be extrapolated for the post closureperiod of performance. This effort should take no more than 4 person weeks.

10) Exploratory shaft facility design. This topical report should discussconstruction monitoring that should take place during ESF construction,construction specifications, and evaluation of adverse impacts of constructionon repository construction. This effort should take no more than 6 personweeks.

11) Discontinuum vs. Continuum analyses for NNWSI. This topical report shouldInvestigate the use of continuum and discontinuum analyses for NNWSI. Thedocument that was prepared for BWIP should be used as a basis for this topicalreport. This effort should take no more than 4 person weeks.

Other work to be performed by ITASCA is as follows:

1) Document review of the MUDEC code and the applicability of usin anImplicit thermal calculation scheme. This review should take no more than10 person days.

2) Review of the draft of the NRC GTP on Anticipated and UnanticipatedEvents and processes. This review should take no more than 5 person days.

3) Prior approval was given for a senior consultant to attend a OA reviewmeeting for the CDSCP draft comments in Rockville, Md. held in lateFebruary, 1988.

4) Two senior engineers should attend a one day workshop on the CDSCPdraft comments which will be held in Washington, D.C. in late March, 1988.

Z - w-

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The action taken by this letter is considered to be within the scope of thecurrent contract NRC-02-85-002. No changes to costs or delivery of contractedproducts are authorized. Please notify me mmediately if you believe thisletter would result in changes to costs or delivery of contracted products. Ican be reached on (301) 492-0534.

Sincerely,

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David H. TktinskyTechnical Review BranchDivision of High-Level Waste ManagementOffice of Nuclear Material Safety

and Safeguards

cc: E. Knox, NRC